Diesel common-rail high-pressure pumps are customarily designed nowadays with a steel housing or an aluminum housing and with an independent camshaft or eccentric shaft.
DE 10 2007 002 729 B3 discloses a fuel pump for injection systems of internal combustion engines and production methods for said fuel pump. Said fuel pump comprises a pump housing with a predetermined installation position. Said pump housing contains one or more pump units and intake-side nonreturn valves which are assigned in each case to the pump units and, at a predetermined opening pressure, each open to let fuel into the assigned pump unit. Each pump unit comprises a pump piston guided in the pump housing in the radial direction with respect to the drive shaft. Upon rotation of the drive shaft, said pump piston is driven by the eccentric shaft section of said drive shaft and by an eccentric ring through which said shaft section passes, to perform a radial reciprocating movement.
Even in the case of small diesel engines, use has recently been made of plug-in pumps which are driven by a camshaft already present in the engine.
WO 2007/045373 A1 discloses a plug-in pump injection system of an internal combustion engine, in which a plug-in pump designed as an injection pump is assigned to each cylinder of the internal combustion engine. Each plug-in pump has a pump housing with a fuel entry duct and a fuel return duct. An annular plate is arranged in the region of the fuel return duct of each plug-in pump, said plate being provided with recesses and engaging in an encircling groove of the pump housing of the respective plug-in pump, the groove forming part of the fuel return duct.
DE 100 58 057 A1 discloses a method for more rapidly heating an internal combustion engine in a starting phase. In this method, the internal combustion engine is supplied with fuel via injectors, wherein the fuel is compressed by a high-pressure pump and conveyed to the injectors, and wherein at least one pressure regulating valve is provided in a high-pressure line between the high-pressure pump and injectors, the outlet of which pressure regulating valve is connected to a tank and which serves to regulate the fuel pressure at the injectors. The fuel which is dispensed at the outlet of the pressure regulating valve and is conducted to the tank is conducted via a heat exchanger. The latter is connected into a cooling circuit of the internal combustion engine in the starting phase of the internal combustion engine and dispenses the excess heat therefrom via the cooling circuit to the cooling water of the internal combustion engine. The high-pressure pump can be combined with the pressure regulating valve and a precompression valve or volumetric flow regulating valve to form a constructional unit.
Furthermore, it is already known to provide a pre-supply pump on the suction side of a fuel high-pressure pump to raise the pressure by a number of bar and to integrate said pump into the housing of the fuel high-pressure pump. Depending on the application, said integrated pre-supply pump is a self-priming pump, or an additional pump is necessary in order to be able to compensate for pressure losses arising between the fuel tank and the pre-supply pump, i.e. in order to be able to maintain a desired minimum pressure. The additional pump may be an electric pump which is provided in the fuel tank.
If the fuel high-pressure pump does not have an independent pump housing and if the camshaft of the motor vehicle is used for driving the piston or plunger of the fuel high-pressure pump, then the above-described integration of a pre-supply pump is no longer possible, and instead an independent electric pre-supply pump is used.